Industrial pollution has been suspected as a cause of non-Hodgkin lymphoma (NHL) particularly because the rates of this cancer increased dramatically during the latter half of the 20th century, lagging slightly behind a period of expanded industrial production in the United States. Despite a compelling hypothesis, there have been few rigorous studies which examined the association between NHL and specific industrial pollutants. Such studies are becoming more readily implemented with the increasing availability and ease-of-use of desktop geographic information systems (GIS) and public databases of industry location and emissions. The investigators propose a case-control study of long-term environmental exposure to industrial pollutants and risk of NHL. Subjects for the proposed study are cases (n=855) and controls (n=781) from an existing NCI-sponsored multi-site study, recruited from Los Angeles County and the Seattle and Detroit metropolitan regions. Residential histories will be used to characterize the location of subjects during the 30-year time period of etiologic interest. A geodatabase will be created for exposure assessment purposes, to contain information on industries including location, operation type, and emissions, as recorded in various sources including the Environmental Protection Agency's Toxics Release Inventory (TRI) and historical business directories from California, Washington, and Michigan States. We will examine NHL risk in relation to specific types of industry, including petroleum refining and pulp and paper mills. The risk associated with specific industrial pollutants of interest, including solvents, polycyclic aromatic hydrocarbons, and dioxins, will be examined after developing exposure contours based on emissions quantities and meterologic data. The study's wealth of existing data on long-term residential history and potential confounders, in addition to the use of GIS for development of detailed exposure metrics, will enable the investigators to make a useful contribution to the current state of knowledge regarding environmental causes of NHL.